(a) Field of the Invention
The present invention relates to a printer guide member with improved wear resistance, and, more particularly, to a guide member suitably adapted as a printer wire guide for a dot matrix printer.
(b) Description of the Prior Art
A dot matrix printer selectively moves a plurality of print wires and urges them onto printing paper to print desired information. A printer of this type has a wire guide member for holding the respective printer wires at predetermined intervals. For this purpose, the wire guide member has a plurality of aligned guide holes through which the printer wires are movably inserted.
In the wire guide member, the printer wires move very frequently and in sliding contact with the guide holes. When the guide holes wear and the hole diameters increase due to such frequent movement of the printer wires, the printer wire holding positions are rendered unstable or deviate from the normal positions, thus degrading the printing quality. In view of this problem, in order to hold printer wires stable in a wire guide member, the member must have wear resistance to prevent wear of guide hole portions.
Printer wires normally comprise piano or tungsten wires. High-quality printer wires comprise tungsten carbide (WC). For printer wires made of such materials, it has been proposed to manufacture a wire guide member consisting of alumina (Al.sub.2 O.sub.3) ceramic or sapphire.
However, a wire guide member made of such a material has only a limited wear resistance when accompanied by increases in both printing speed and the number of printing operations performed by the printer wires. Thus, upon exceeding a predetermined printing speed or a predetermined number of printing operations, the guide holes wear significantly and the wire guide member cannot then be used.
Along with high-speed processing demands in computers, a high printing speed is also required for a dot matrix printer. In order to improve printing precision, the number of pins tends to be increased. However, a conventional wire guide member cannot provide satisfactory durability under conditions of such an increase in both the printing speed and the number of pins.